Cartilage is a flexible connective tissue found in the joints between bones, the rib cage, the ear, the nose, the bronchial tubes, the pubic symphysis, and the intervertebral discs. Cartilage is not as hard and rigid as bone but is stiffer and less flexible than tendons and ligaments. Cartilage is made by specialized cells called chondroblasts that produce a large amount of extracellular matrix composed of collagen fibers, abundant ground substance rich in proteoglycan, and elastin fibers. Cartilage is classified in three types, elastic cartilage, hyaline cartilage and fibrocartilage, which differ in the relative amounts of these three main components. Chondroblasts that get caught in the matrix are called chondrocytes. They reside in spaces called lacunae with up to eight chondrocytes per lacuna.
Unlike other connective tissues, cartilage does not contain blood vessels. The chondrocytes are supplied by diffusion, which is helped by the pumping action generated by compression of the articular cartilage or flexion of the elastic cartilage. Because it does not have a direct blood supply, compared to other connective tissues, cartilage grows and repairs much more slowly. As a result, when cartilage is injured or diseased, it is very difficult to heal. It is believed that a treatment option that could prevent the development of cartilage disorders and diseases, accelerate healing of cartilage once injured or diseased, perhaps eliminating the need for surgical intervention in severe cases, is desirable. Accordingly, it is an object of the instant invention to provide such a treatment option to subjects suffering from cartilage diseases, disorders and injuries including, but not limited to, degenerative disc disease.